If the problem has been going on for months, infection is not likely. If only one is affected, allergies are not likely. If the eye is not inflamed and she is not squinting, glaucoma is not likely. The runny eye can be caused by a blocked tear duct or decreased tear production. In a horse this age, a cure may not be possible. Plain saline used for contact lenses or artificial tears can be used to flush the eye 3-4 times a day. If the problem persists, tear production should be measured. A eye medicine with any anti-inflammatory may be needed if the tear duct is occluded. There no OTC meds that will have one in them. The eye may also need to be stained to rule out corneal injury at this point. I would try flushing the eye several times a day prior to using the eye meds you have. If the problem persists, you need stronger meds and tests from your vet to get a specific diagnosis and treatment plan.

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